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Thread: Voltage values for domestic installation for a COC.

  1. #1
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    Voltage values for domestic installation for a COC.

    Hi All

    When doing the testing on a domestic single phase installation, are there any calculations needed to be done as far as acceptable voltage and volt drop is concerned ?

    The reason I ask is that there are basically 4 voltages that have to comply, that can be measured with a voltmeter:

    1. Voltage between neutral & earth.
    2. No load voltage at Main switch on distribution board.
    3. On load voltage at Main switch on distribution board.
    4. Voltage at available load.

    My query is regarding the values of points 3 and 4 above.

    SANS 10142-1 in 8.7.11 and 8.7.12 describes in detail how to measure these voltages ( no calculations involved ). It also says " record the values obtained on the test report "

    Now we come to the test report itself and it asks for the above voltages "as calculated for full load"

    My question is: Must we measure the voltage as per the book ? or
    Must we calculate the voltage as per the test report ?

    Any thoughts ?

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    Measuring will be much easier and save time and i hope calculating will also give u the same values

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    Red face

    HI

    I see you are working from an old edition of SANS 10142.

    In my opinion in a domestic type installation it is easier to plug in a 50% load and measure the voltage as the majority of time it is going to be a 20 Amp CB on the possibly worse circuit.

    In a complex installation like a shopping center , industrial type installation it may not be possible to connect a 50% rated load and then it would be necessary to perform the calculations as per Annex D ( SANS 10142-2 clause 8.6.11) - Especially to Shop DB's and plant rooms.

    The SANS regulation gives you a choice and is what the test report is based on - Obviously the compilers of the test report could not find sufficient space to write out the complete clause and decided to rather confuse everyone by writing a short version.

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    Thank you GCE

    Actually I have the new edition that is kept in the bakkie with me ( Edition 2 )

    Edition 1.8 is in the office and I used that one to reference the regulation. I see the reg number has changed from 8.7 to 8.6

    I only work on domestic installations and have been using the 50% load and measuring method for yonks.

    Glad that what I've been doing seems to be acceptable.

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